The prior art shows a number of wooden and molded plastic frame structures having interlocking back panels for holding an object to be displayed within the frame, such as pictures, signs, mirrors and the like. Esry U.S. Pat. No. 3,782,015 is directed to a display frame having an outer shell with a transparent face and peripheral vertical sides forming an opening for a display card. A core of corresponding configuration is provided which fits within the sides of the outer shell. A pair of inwardly directed tabs is provided on opposite edges of two of the sides that releasably engage over the back surface of the core. Place, in his U.S. Pat. No. 1,842,285, uses wire pins having bent arcuately contoured heads that engage within slots or holes in the back flanged edge of a molded picture frame to hold the backing sheet thereagainst.
Another illustration is Novak U.S. Pat. No. 2,928,199 which discloses a metal mounting structure for mirrors having a front frame with four L-shaped corner clips that are locked in place by a hook and socket arrangement on the back plate. U.S. Pat. No. 2,116,584 to Shelby shows a ribbed T-lock joint and recess combination for holding sections of wooden pieces together without the necessity of clamping during the drying of glue used in the joints. The Ware U.S. Pat. No. 1,837,348 incorporates a pair of headed studs on the edge of a pedestal that releasably engage a matching pair of key-hole slots in the edge of a frame for holding a display card on or from a horizontal surface. The display frame of Siegel in U.S. Pat. No. 1,692,999 utilizes an interior and exterior frame which fit in a locking arrangement by means of spring-loaded detents or plungers on the periphery of the interior frame which engage recesses in an inner edge of the exterior frame.
The instant invention represents an improvement over these prior art structures as hereinafter described.